ERAPs Reduce In Vitro HIV Infection by Activating Innate Immune Response

Alpha-synuclein shapes monocyte and macrophage cell biology and functions by bridging alterations of autophagy and inflammatory pathways

Introduction: Abnormal spreading of alpha-synuclein (αS), a hallmark of Parkinson's disease, is known to promote peripheral inflammation, which occurs in part via functional alterations in monocytes/macrophages. However, underlying intracellular mechanisms remain unclear. Methods: Herein we investigate the subcellular, molecular, and functional effects of excess αS in human THP-1 monocytic cell line, THP-1-derived macrophages, and at least preliminarily, in primary monocyte-derived macrophages (MDMs). In cells cultured w/wo recombinant αS (1 μM) for 4 h and 24 h, by Confocal microscopy, Western Blot, RT-qPCR, Elisa, and Flow Cytometry we assessed: i) αS internalization; ii) cytokine/chemokine expression/secretion, and C-C motif chemokine receptor 2 (CCR2) levels; iii) autophagy (LC3II/I, LAMP1/LysoTracker, p62, pS6/total S6); and iv) lipid droplets (LDs) accumulation, and cholesterol pathway gene expression. Transwell migration assay was employed to measure THP-1 cell migration/chemotaxis, while FITC-IgG-bead assay was used to analyze phagocytic capacity, and the fate of phagocytosed cargo in THP-1-derived macrophages. Results: Extracellular αS was internalized by THP-1 cells, THP-1-derived macrophages, and MDMs. In THP1 cells, αS induced a general pro-inflammatory profile and conditioned media from αS-exposed THP-1 cells potently attracted unstimulated cells. However, CCL2 secretion peaked at 4 h αS, consistent with early internalization of its receptor CCR2, while this was blunted at 24 h αS exposure, when CCR2 recycled back to the plasma membrane. Again, 4 h αS-exposed THP-1 cells showed increased spontaneous migration, while 24 h αS-exposed cells showed reduced chemotaxis. This occurred in the absence of cell toxicity and was associated with upregulation of autophagy/lysosomal markers, suggesting a pro-survival/tolerance mechanism against stress-related inflammation. Instead, in THP-1-derived macrophages, αS time-dependently potentiated the intracellular accumulation, and release of pro-inflammatory mediators. This was accompanied by mild toxicity, reduced autophagy-lysosomal markers, defective LDs formation, as well as impaired phagocytosis, and the appearance of stagnant lysosomes engulfed with phagocytosed cargo, suggesting a status of macrophage exhaustion reminiscent of hypophagia. Discussion: In summary, despite an apparently similar pro-inflammatory phenotype, monocytes and macrophages respond differently to intracellular αS accumulation in terms of cell survival, metabolism, and functions. Our results suggest that in periphery, αS exerts cell- and context-specific biological effects bridging alterations of autophagy, lipid dynamics, and inflammatory pathways.

Endoplasmic reticulum aminopeptidase 2 regulates CD4+ T cells pyroptosis in rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic, progressive autoimmune disease with a complex pathogenesis that has not yet been fully elucidated, and T-cell pyroptosis is an important pathogenetic factor in RA. This study aimed to investigate the role of endoplasmic reticulum aminopeptidase 2 (ERAP2) in the pyroptosis of CD4+ T cells in RA and the specific molecular mechanism.

METHODS

Peripheral venous blood was collected from human subjects, and CD4+ T cells were isolated and activated to measure the level of pyroptosis and ERAP2 expression. Pyroptosis levels were assessed using immunofluorescence, flow cytometry, qRT-PCR, and Western blotting. Changes in pyroptosis levels were observed upon knockdown or overexpression of ERAP2. To detect activated Caspase-1 in tissues, chimeric mice were engrafted with human synovial tissue and reconstituted with human CD4+ T cells. CD4 + T cells were treated with GLI1 antagonists and SMO receptor agonists to detect changes in pyroptosis levels.

RESULTS

CD4+ T cell levels undergoing pyroptosis were found to be elevated in the blood and synovium of RA patients. The gene and protein expression of ERAP2 were significantly higher in CD4+ T cells from RA patients. Deletion of ERAP2 suppressed pyroptosis of these cells, attenuated the activation of Caspase-1 in tissue T cells, and reduced tissue inflammatory responses. Reciprocally, overexpression of ERAP2 triggered inflammasome assembly, activated Caspase-1, and induced pyroptosis in CD4+ T cells. Mechanistically, ERAP2 inhibits the Hedgehog signaling pathway and upregulates the expression of nucleotide-binding oligomerization segment-like receptor family 3(NLRP3), cleaved Caspase-1, and Gasdermin D to promote pyroptosis in CD4+ T cells.

CONCLUSIONS

Taken together, our results identify a novel mechanism by which ERAP2 regulates RA development and document the effect of the ERAP2/Hedgehog signaling axis on pyroptosis of CD4+ T cells from RA patients.

The role of endoplasmic reticulum aminopeptidases in type 1 diabetes mellitus

Type-I diabetes mellitus (T1DM) is generally considered as a chronic, T-cell mediated autoimmune disease. This notwithstanding, both the endogenous characteristics of β-cells, and their response to environmental factors and exogenous inflammatory stimuli are key events in disease progression and exacerbation. As such, T1DM is now recognized as a multifactorial condition, with its onset being influenced by both genetic predisposition and environmental factors, among which, viral infections represent major triggers. In this frame, endoplasmic reticulum aminopeptidase 1 (ERAP1) and 2 (ERAP2) hold center stage. ERAPs represent the main hydrolytic enzymes specialized in trimming of N-terminal antigen peptides to be bound by MHC class I molecules and presented to CD8+ T cells. Thus, abnormalities in ERAPs expression alter the peptide-MHC-I repertoire both quantitatively and qualitatively, fostering both autoimmune and infectious diseases. Although only a few studies succeeded in determining direct associations between ERAPs variants and T1DM susceptibility/outbreak, alterations of ERAPs do impinge on a plethora of biological events which might indeed contribute to the disease development/exacerbation. Beyond abnormal self-antigen peptide trimming, these include preproinsulin processing, nitric oxide (NO) production, ER stress, cytokine responsiveness, and immune cell recruitment/activity. The present review brings together direct and indirect evidence focused on the immunobiological role of ERAPs in T1DM onset and progression, covering both genetic and environmental aspects.

Evolution of immune genes is associated with the Black Death

Infectious diseases are among the strongest selective pressures driving human evolution1,2. This includes the single greatest mortality event in recorded history, the first outbreak of the second pandemic of plague, commonly called the Black Death, which was caused by the bacterium Yersinia pestis3. This pandemic devastated Afro-Eurasia, killing up to 30-50% of the population4. To identify loci that may have been under selection during the Black Death, we characterized genetic variation around immune-related genes from 206 ancient DNA extracts, stemming from two different European populations before, during and after the Black Death. Immune loci are strongly enriched for highly differentiated sites relative to a set of non-immune loci, suggesting positive selection. We identify 245 variants that are highly differentiated within the London dataset, four of which were replicated in an independent cohort from Denmark, and represent the strongest candidates for positive selection. The selected allele for one of these variants, rs2549794, is associated with the production of a full-length (versus truncated) ERAP2 transcript, variation in cytokine response to Y. pestis and increased ability to control intracellular Y. pestis in macrophages. Finally, we show that protective variants overlap with alleles that are today associated with increased susceptibility to autoimmune diseases, providing empirical evidence for the role played by past pandemics in shaping present-day susceptibility to disease.

To Be or Not to Be: The Case of Endoplasmic Reticulum Aminopeptidase 2

To be, or not to be, that is the question. (William Shakespeare, Hamlet)

Endoplasmic reticulum aminopeptidases 1 and 2 (ERAP1 and ERAP2, respectively) play a role in trimming peptides that are too long to be bound and presented by class I HLA (HLA-I) molecules to CD8⁺ T cells. They may also affect the HLA-I-presented peptide repertoire by overtrimming potential epitopes. Both enzymes may also be released from the cell to cleave cytokine receptors and regulate blood pressure. Both enzymes are polymorphic, which affects their expression, specificity, and activity, resulting in their role in diseases associated with HLA-I. In this brief review, we concentrate on ERAP2, less investigated because of its lack in laboratory mice and 25% of humans, as well as a lower polymorphism. ERAP2 was found to be associated with several diseases and to influence ERAP1 effects. It was discovered recently that the defective ERAP2 gene, not encoding functional aminopeptidase, may nevertheless, during viral infections, produce a truncated protein isoform of unknown function, possibly interfering with ERAP1 and full-length ERAP2 by heterodimer formation. The disease associations of ERAP2, alone or in combination with ERAP1, are reviewed.